Effect of immunocastration on some key technological ...

Effect of immunocastration on some key technological and sensory quality parameters of Italian typical dry-cured ham Roberta Virgili1, Anna Pinna1, Cristina Schivazappa1, Giuseppe Minelli2, Giordano Ventura2, Claudio Guarini3 (1) SSICA, Parma (2) Vet practitioners (3) Zoetis Italia Italy 1. Introduction The objective of this study was to evaluate the effects of the vaccine against boar taint, used as a more welfare-friendly alternative to surgical castration in heavy male pigs (Bonneau & Prunier, 2005; Lundström & Zamaratskaia, 2006), on Parma dry cured ham quality. Until now no investigation has covered the subject of Italian typical dry cured hams. This paper will focus on the most significant outcomes of both fresh and dry-cured ham quality parameters. 2. Materials and methods 2.1 Pigs Forty piglets were randomly assigned to two groups of twenty, identified respectively as control (C) and treated, i.e. vaccinated against boar taint (T). Group T pigs were vaccinated against Gonadotrophin Releasing Factor (produced by Zoetis) at the age of 10-11 weeks, at 26-27 weeks and then at 36-37 weeks , whereas the untreated pigs (C) were surgically castrated within 7 days from birth. Pigs were slaughtered in the same slaughter house at 40-41 weeks, with an average live weight of 165 Kg. 2.2 Fresh legs Carcasses were sectioned soon after slaughtering (hot-cutting), and the legs were subjected to established measurements at the slaughterhouse, taken either at their removal from carcass or after one day of chilling. Evaluations are described in Table 1. Table 1. Measurements made on legs at slaughter house.

Measurement

Description

Hot weight

Weight (kg) of the hot-sectioned leg

Refrigerated weight

Weight (kg) of the refrigerated leg

Trimmed weight

Weight (kg) of the refrigerated ham after trimming

Fat thickness

Thickness of fat layer covering the ham (cm), measured below femur head

Some meat quality parameters were also evaluated. Refrigeration weight loss was measured as the loss of weight (%) of green hams (hot weight, Table 1) after 24 hours

refrigeration in chilling rooms working at 0-2°C. It was calculated as: [(Hot weightRefrigerated weight) / Hot Weight] ×100. pH of the refrigerated hams was measured in the semimembranous muscle at 24h after slaughter by a portable pH meter WTW pH330 equipped with a Hamilton glass electrode previously calibrated at pH 4.0 and 7.0. Meat samples were obtained from the semimembranosus muscle of each left leg at 24h after slaughter and analysed for proteolytic activity as cathepsin B activity (Barrett and Kirschke, 1981). Results were expressed as nmoles of AMC min-1 x g of muscle-1. 2.4 Dry-cured hams All legs were dry cured according to Parma ham manufacturing guidelines (Protected Designation of Origin Specifications and Dossier pursuant to Council Reg. EEC n°2081/92 of 14 July 1992), and matured until 15 months of ageing. Weight loss was reported as the difference between trimmed ham weight and weight of ham at the end of maturation process, expressed as per cent of trimmed ham weight (Table 1). At the end of the process, all hams were qualified for receiving the Parma ham brand, having proved to be in compliance with regulatory requisites. Then, dry-cured hams were deboned, sectioned and a portion of biceps femoris muscle was taken and kept refrigerated under vacuum until chemo-physical analyses were performed. An additional sample, consisting of a large central slice (10 cm thickness) comprising the three main muscles (semimembranosus, biceps femoris and semitendinosus) was stored refrigerated for sensory analyses. C and T groups were each represented by 20 dry-cured hams, coming from 20 pigs. 2.4.1 Chemo-physical and sensory analyses Chemo-physical analyses included protein, moisture and salt by reference methods (AOAC 2002a, b; AOAC 1995), water activity measured by LabMaster (Novasina), according to International Standard ISO/FDIS 21807 (2004) and the proteolysis index, as measured after protein precipitation with 10% trichloroacetic acid (Careri et al., 1993). Sensory analyses were performed by descriptive testing of dry-cured hams at 15 months of ageing, following general guidelines for this kind of test (UNI EN ISO 13299:2010). The panel, made up of six trained subjects, was asked to quantitatively assess the samples for gustatory and olfactory descriptors related to boar taint. Each descriptor had to be scored on a 0-9 intensity scale, with the scale extremes corresponding to absence and maximum perceivable intensity of the attribute, respectively. At each testing session, two hams were randomly chosen from C and T groups, and the samples were presented to panelists in a balanced order (Macfie, Bratchell, Greenhoff, & Vallis, 1989).

The hams were presented in thin slices, obtained by a slicing machine set to deliver slices 1mm in thickness. 2.5 Statistical analysis Summary statistics of data from this study were obtained by the Descriptive procedure of SPSS ver. 20 statistical package. The effect of the treatment group (surgically castrated as controls and three treatments with vaccine against boar taint) was analysed applying the General Linear Model procedure (GLM) of SPSS ver. 20 statistical package.

3 Results and discussion 3.1 Fresh legs Results from measurements taken at the time of slaughtering are summarised in Table 2, where the mean values for T and C groups are compared. Both fresh and refrigerated leg weights from treated pigs did not show differences from the control group. This finding is not in agreement with similar data from other authors (Font I Furnols et al., 2012, Pauly et al., 2009 and Fuchs et al., 2009), who reported greater weights in vaccinated pigs; however, it is to be stressed that pigs from the cited investigations were slaughtered earlier in age than those of the present study (6-7 months vs 9-10 respectively), which were slaughtered according to the Tutelary Regulations stating a minimum slaughtering age of 9 months for pigs to be processed into Parma hams (Protected Designation of Origin Specifications and Dossier pursuant to Council Reg. EEC n°2081/92 of 14 July 1992). However, also in the present study, on average, treated pigs showed an increase in weight of fresh legs, although not significantly differing from controls (P>0.05). The hams from the treated pigs showed a covering fat thicker (P=0.04) than the control animals, a likely consequence of the average weight increase achieved in fresh hams of T group. Table 2. Measurements made on fresh legs at the slaughter house. Least Square Means (LSM) for control (C) and treatment (T) groups and P-values are reported.

C

T

P-value

Fresh weight (kg)

16.7

17.1

0.20

Refrigerated weight (kg)

16.5

16.9

0.24

Trimmed weight kg

13.1

13.3

0.43

Fat thickness (cm)

2.3

2.6

0.04

With regard to parameters related to meat quality, none of the variables under investigation showed differences (P>0.05). Cathepsin B activity, regarded as an indicator of proteolytic potential, showed a slightly lower average value in surgically castrated, without statistical significance (P=0.10). No difference (P>0.05) between groups was found for pH24h, showing that castration, achieved either surgically or immunologically, yielded similar pH24h in semimembranosus muscle. Table 3. Refrigeration weight loss, pH24h and cathepsin B activity of fresh legs. Least Square Means (LSM) for control (C) and treatment (T) groups and P-values are reported.

C

T

P-value

Refrigeration weight loss, %

1.3

1.4

0.10

pH24h

5.66

5.70

0.35

Cathepsin B1

1.2

1.3

0.10

1

Enzyme activity in nmoles of aminomethylcoumarin (AMC) x min-1 x gram muscle-1

3.3 Dry-cured hams The final weight loss measured at the end of the maturation process (15 months), does not show a difference (P>0.05) between the two groups, though the trend shows a more marked weight loss in hams from control pigs (Table 4). 3.3.1 Chemo-physical and sensory analyses Chemical composition and water activity values of biceps femoris muscle (Table 4) removed from 15-months old dry-cured hams fall in the range expected for Parma hams of the same age (Benedini et al., 2012). No differences between groups are found for any of the variables under examination. It is evident from these data, and relevant to the present investigation, that the vaccination treatment does not result in enhanced protein hydrolysis when compared with conventional surgical castration. This occurrence is in agreement with pH24h, Cathepsin B and salt values (main factors affecting final proteolysis in drycured ham), reported in Tables 3 and 4 for control and treatment groups (Schivazappa et al., 2002). Sensory analyses were run with the purpose to assess whether dried hams from vaccinated pigs can be distinguished from control hams as far as boar taint is concerned. Dried hams at 15 months of ageing underwent quantitative descriptive analysis by a trained panel who scored them for boar taint perception. Results (Table 4) show that boar taint descriptors (odour and taste) were weakly perceived both in the treatment and in the control group.

Table 4. Weight loss, chemophysical and sensory analyses on dry-cured hams. Proximate composition (percent values) are measured in biceps femoris muscle. Least Square Means (LSM) for control (C) and treatment (T) groups and P-values are reported.

C

T

P-value

31.6

31.1

0.09

Aw

0.901

0.903

0.31

Fat

3.4

3.9

0.36

Protein

29.1

29.1

1.00

Moisture

59.1

59.1

0.95

Salt

6.5

6.4

0.47

Proteolysis index

31.2

30.6

0.30

Olfactory boar taint 1.0

0.9

0.74

Gustatory boar taint 1.1

0.9

0.31

Final weight loss Chemo-physical

Sensory

Conclusions Vaccination against boar taint based on three treatments proved to be effective for Italian heavy pigs tested in the present investigation, because no significant difference was found between treated and surgically castrated pigs in considered quality traits of fresh and drycured hams. Further work is in progress to evaluate the effect of different treatments on other carcass cuts. References AOAC. 2002a. Method 928.08. Protein content. In Official Methods of Analysis, 17th Ed., Assoc. of Official Analytical Chemist, Gaithersburg, Maryland. AOAC. 2002b. Method 950.46. Moisture content in meat. In Official Methods of Analysis, 17th Ed., Assoc. of Official Analytical Chemist, Gaithersburg, Maryland. AOAC. 1995. Method 935.47. Salt (chlorine as sodium chloride) in meat. In Official methods of analysis, 16th Ed., Assoc. of Official Analytical Chemist, Gaithersburg, Maryland. Barrett, A. J., and H. Kirschke, H. (1981). Cathepsin B, Cathepsin H and cathepsin L. Page 541 in Methods in Enzymology. S. P. Colowick and N. O. Kaplan, ed. Academic Press, Inc., New York.

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